1. Field of the Invention
This invention relates to a laminated capacitor and particularly to improvements in an arrangement for providing a laminated capacitor with a fuse function.
2. Description of the Prior Art
A conventional typical laminated capacitor construction is shown in FIGS. 10 and 11. This laminated capacitor 4 comprises a plurality of internal electrodes 1 formed in a laminated state, with dielectric layers 2 held each between adjacent internal electrodes 1 to give capacitance. A first set of internal electrodes 1 are formed to extend to one of the respective end edges of the dielectric layers 2, while a second set of internal electrodes 1 are formed to extend to the other end edges of the dielectric layers 2. Such internal electrodes 1 are arranged so that the first and second sets of internal electrodes alternate with each other. Opposed end surfaces of the dielectric laminated structure comprising laminated dielectric layers 2 are formed with external electrodes 3. One of these external electrodes 3 is electrically connected to the first set of internal electrodes 1, and similarly the other is electrically connected to the second set of internal electrodes 1.
In the laminated capacitor 4, if one dielectric layer 2 has defects, such as formation of voids, a short often forms between internal electrodes 1 which are positioned on the opposite surfaces of said particular dielectric layer 2. If such short occurs, the capacitor 4 immediately stops functioning as such, resulting in the problem of adversely affecting the entire device using such capacitor 4.
To solve this problem, there is proposed a laminated capacitor 6, as shown in FIG. 12, wherein to maintain the open mode in the circuit using this capacitor 4 even if the capacitor 4 is broken down as described above, a fuse 5 is attached to the outside (U.S. Pat. No. 4,193,106).
However, the laminated capacitor 6 shown in FIG. 12 requires not only the labor of attaching a fuse 5 separately but also the labor of connecting said fuse 5 between one external electrode 3a and associated ones of internal electrodes 1a. To this end, it is necessary to form an intermediate electrode 7, besides a pair of external electrodes 3a, on an outer surface of the dielectric laminated structure. As for particular ones of internal electrodes 1a to be formed on the dielectric layers 2a, it is necessary to change their patterns so that they are electrically connected to the intermediate electrode 7. Such labor and change in design involve an increase in the cost of the capacitor 6. Further, if a breakdown as described above takes place in the capacitor 6 and the fuse 5 blows, this capacitor 6 no longer functions as such. Further, since the capacitor 6 has the intermediate electrode 7 formed thereon, limitations in the direction of the capacitor 6 are sometimes encountered when the capacitor 6 is to be mounted on a printed circuit board. Since the fuse 5 is connected in series to the capacitance provided by the capacitor 6, there is a problem that an equivalent series resistance which appears between the pair of external electrode 3 of the capacitor 6 increases undesirably.